Process for electroplating.



THOMAS A. EDISON, OF LLEWELLYN PARK, ORANGE, NEW JERSEY.

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Specification of-I etters Patent. Application filed March 19, 1906.Serial No. 306,781.-

Patented July 12, 1910.

To all whom it may concern:

' Be it known that 1,1IKO1WIAS A. EDISON, a

citizen of the United States, residing at Llewellyn Park, Orange, countyof Essex,-

and State'of New Jersey, have invented a certain new and useful Processof Electroplating, of which the following is a description.

In carrying on experimental and commercial operations in connection withelectro= plating, I find that the occlusion of hydrogen tends to makethe deposit somewhat brittle and more or lessporous, and that hydrogengas clings to the surfaces of the deposited metal in the form of veryfine bubbles, thereby making the surfaces more or. less warty and rough.The presence of occluded hydrogen, aswell as of the hydrogen bubblesreferred to, prevents the deposition at a high rate, and also results inStreaky and uneven deposits.

My object is to provide an imprloved process of electroplating, wherebyI very largely eliminate the occlusion of hydrogen, as well as theformation of hydrogen bubbles on the deposited surfaces, and inconsequence I am enabled to carry on a plating operation at a muchhigher rate than is now possible, and

at the same time with the production of a better quality of deposit,less brittle in character, practically free of pores, andwith a smoothand uniform surface.

' The invention resides in the fact that by maintaining in the platingbath a small quantity of material which will combine with the hydrogen,for example, free chlorin, the latter will combine with any hydrogen setfree by the electrolytic action, or otherwise, thereby preventing theformation of metallic hydrates as well as the occlusion of thegas, andeliminating also the appearance of microscopic bubbles thereof, whichcling to the deposited surfaces with the objections-pointed out. Whenfree chlorin is thus presentinthe bath, it combines with any hydrogengenerated therein to form hydrochloric acid, although it is possiblethat other favorablereactions may be brought about by the presenceoffree chlorin. The chlorin may be added to the plating bath inanysuitable way, such, for example, as by passing the gas continuously,or at suitable intervals, through the bath; by adding to thebath,watersaturatedwith chlorin, or by adding from time-"t0 timefresh-quantities of'the electrolyte saturatedwith chlorin. For.instance,if copper is to be plated from a. solution of sulfate of copper, thechlorin can be added by chlorinating a suitable quantity of .-thesolution, which can be added from time to time in small amounts to thesolution as the chlordn becomes exhausted. In practice, the solutionshould have alslightly acid re.- action. I find that the eflect of thechlorin thus introduced into the bathlasts for several hours, when afresh quantity must be added. In the case of a. chlorid bath (for carbonanode of very small surface can be connected to the metallic anode andmade to continuously ehlorinate thesolution, as will be understood;Practically all of the chlorin,is utilized in combining with 'thehydrogen developed, there being very little loss of chlorin by itscombination with either the anode or cathode. "Free bromin may also beemployed, but with results that are far inferior to those secured whenchlorin is used. The use of chlorin in cobalt plating baths isespecially beneficial, and this is particularly true when cobalt-chloridsolutions are employed.

Having now described my invention, wha't I claim as newand desire tosecure by Letters Patent is as follows 1. That improvement in the art ofelectroplating which consists in chlorinating a suitable quantity ofcopper sulfate solution, and adding from time to time in small amountsto thesolution in a copper. plating bath, 'as'the chlorin becomesexhausted by reaction with the hydrogen developed upon the cathode,substantially as set forth.

, 2. That improvement in the art of electro-plating which consists inchlorinating asuitable quantity of copper 'sulfate solution and addlngfrom time to time in small amounts to thmsolution in a copper'platingbath,;as the chlorin becomes exhausted by reaction with the hydrogendeveloped upbn slightly acid, substantially as set forth. the cathode,substantially as set forth. 10 3. That improvement in the art of elec-This specification signed and witnessed tro lating which consists inhalogenizing a this 24th day of Febry 1906. 5 suitable quantity ofcopper sulfate solution, THOMAS A. EDISON. and addlng from time to timein small Witnesses: amounts to the solution in a cop er plating FRANK L.DYER,

bath, as the ,halogen becomes ex austed by ANNA R. KLEH the cathode, thesolution being maintained reaction with the hydrogen developed upon

